Process and apparatus for cracking mineral oil



July 24, 192s.

FIG. 2

FIG. 1

1,678,126 J. M. scHooNMAKER, .JR

PROCESS AND APPARATUS FOR CRACKING MINERAL OIL Patented July 24, 1928.

UNITED STATES PATENT OFFICE.

JAMES M. SCHOONMAXER, JR., OF SEWICKLEY, PENNSYLVANIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE TEXAS COMPANY, OF NEW YORK, N. Y., A CORPORATION 0F v DELAWARE.

PROCESS AND APPARATUS FOR CRACKING MINERAL OIL.

Application led Hay 15, 1922, Serial No. 560,988. Renewed .Tune 3, 1925.

My invention relates to the production of light hydrocarbons suitable for motor fuel from the heavier fractions of petroleum 011s by the process of thermal decomposition and liy molecular rearrangement known as pyrolysis or crackin 'lhe general ob]ect of my invention is to treat relatively heavy hydrocarbons in such a way as to produce therefrom a greater l@ quantity oi light hydrocarbons of the gasoline type than can be produced by the cracking methods heretofore known.

.ds a subsidiary object, my invention aims to so conduct the cracking operation as to lli reduce the deposit of carbon'in the cracking zones, thus enabling a given apparatus to run continuously lor a long time Without cleaning.

My invention is based upon the following discoveries:

l. ldvery petroleum oil or traction has a quite definite critical temperature, tor any given pressure, below `which cracking does not take place to any considerable extent and @t above which cracking proceeds rapidly.

2. This critical cracking temperatureincreases with increase in pressure up to a point which, depending on the oil used, is trom l@ F. to 50 l7`.yabove the temperature at which the oil begins to crack at normal pressure. ln other words, the critical cracking temperature may be raised by the application oil pressure through a range ot to 3. A temperature exists in every oil or traction beyond which temperature no practicable increase in pressure vvill prevent substantial cracking. I'lbis point may be termed the maximum critical cracking temperature or that particular oil. These critical points vary with diderent oils and with diderent fractions oli the same oil, but are quite delinite in ordinary oil attractions.

ll. li an oil is heated to a temperature between its cracking point under normal or low pressures and its maximum critical cracking point as above dened, under pressure suilicient to prevent substantial cracking, and is then suddenly allowed to expand, cracking occurs with almost explosive rapidity. This cracking reaction is pro lill moted bythe addition of heat to the oil at the moment oi expansion sufficient toat least restore the heat lost through expansion.

l consider that While the oil is being heated up to the critical cracking point under any given pressure, the hydrocarbon molecules are brought to a condition of internal strain which tends to disrupt the molecules when the critical temperature is passed. This disruptive tendency may, as stated above, be suppressed by subjecting the oil to high pressure, the pressure necessary for this purpose being greater for lighter fractions than for heavier fractions. Therefore, an oil may be heated to the critical cracking temperature of its heaviest fractions Without producing any appreciable cracking, provided that the oil is maintained under suiiicient pressure, While being heated, to prevent the lighter fractions trom decomposing., 'lhis pressure also prevents substantial vaporization ot the oil.

Any liquid heated under pressure will tend to remain a liquid, provided that the pressure is sucient; but when that pressure is suddenly released, the. liquid will tend to disrupt itself into iniinitesimally small particles. 'llhis division places it in a state Where it can 'be most advantageously acted onby additional heat, since the surface area oi the particles ont liquid is multiplied many times. Also, il the liquid brought to this 'condition is ot such a nature that it is subject tochernical decomposition by the application oi heat, it may be heated to some critical temperature Where actual decomposition does not take place, but Where the addition oit heat, simultaneously with the line division ai the liquid through expansion, will cause chemical decomposition.,

li' a hydrocarbon oil, previously heated above its normal critical temperature, and be low its maximum critical cracking temperature as above deiined, under suiicient pressure to prevent cracking, is suddenly lib-- rated into a chamber Where the pressure is materially less, and the temperature is higher, than in the preheating step, the two effects above mentioned will occur. The physical 'disruption or atomizaticn of the liquid Will expose an enormous area for absorbing heat; and this added heat will bring the hydrocarbon molecules above their critical temperature, and will decompose or crack them. The reduction of pressure is accompanied by a drop in the temperature of the oil, due to its expansion, and if such dll Sti

drop in temperature brings any fraction of the oil below its critical cracking temperature no substantial cracking of that fraction will result. If, however enou h heat is added to the oil at the momento expansion to keep the oil at or above its critical tem perature, thorough cracking will occur, and if the oil is kept under these conditions of reduced pressure and high temperature long enough to allow rearrangement of the decomposed hydrocarbons, the maximum yield of cracked products will be obtained.

My present invention takes advantage of the above facts by introducing the oil containing relatively heavy hydrocarbons into an unstabilizing heater where the temperature of the oil is raised to, but not above, the maximum critical cracking temperature of its heavier fractions, thus producing a con.

dition of internal strain in the molecules; preventing both the lighter and heavier molecules from dissociating and from vaporizing at this stage by maintaining the oil under heavy pressure; suddenly relieving the pressure on the heated oil, and adding to the oil. at and after the moment of expansion, sutiicient heat to at least compensate for its drop in temperature through expansion.

The pressure under which the Oil is heated to its normal cracking temperature not only prevents substantial cracking, but also avoids frothing by preventing evolution of gases in this heating zone and maintains in suspension any carbon which may be liberated should a small amount of cracking occur through accident in spite of the existing pressure. When the heated oil, in its condition of unstable equilibrium, is suddenly liberated into the cracking zone, vapors and gases are immediately set free and cause violent turbulence in the cracking zone, thus promoting the cracking reaction, and also keeping most of the liberated carbon in suspension in the turbulent mass of oil. The cracking zone should be somewhat larger in diameter than the pipe or other container in which the unstabilizing heat-ing step is carried out, but is preferably not much larger in diameter than the iirst heating pipe, so that the oil is still in a conined chamber during the expanding and superheating stage.

The pressure which I apply to the oil in the first heating zone is a substantial mechanical pressure as distinguished from the vapor pressure of4 au oil which is generated when the oil is heated above its boiling point in a closed container. The object of this added pressure is notmerely to prevent the oil from vaporizing, but also to inhibit the decomposition or cracking of the oil 'mole cules. y

Another reason for maintainingv high pressure in the first heating zone and loW pressure in the cracking zone is to secure the finest possible division of the oil at the moment of expansion. The greater the pressure drop, the finer the division will be, and the finer the division, the more readily-each particle of oil can be acted upon by the superheat present in the cracking zone. For these reasons, the diiference in pressure between the first heater and the cracking zone should be as great as possible underthe conditions of practical operation. The cracking zone may, with advantage, be kept at a pressure of about 100 pounds per square inch or even at atmospheric or subatmospheric pressure. The oil is discharged from the crackino zone into a separatin chamber, preferably in the natureof a ephlegmating tower, where the oil molecules are given time to complete their rearrangement, with a certain amount of additional cracking, and where the vapors and fixed gases are separated from the tarry residues. The yvapors and gases are then conducted to a condenser, suitably of the refiux type, where the vapors are condensed to produce the gasoline-like product. The formationof fixed gases is reduced if the condenser is kept under constant pressure, and therefore, when the cracking zone and the separating tower are operated at `atmospheric or subatmospheric pressure, or at low superatmospheric pressure, I preferabl employ a. pump between the separating c amber and the condenser in order to raise and keep constant the pressure on the vapors and gases during condensation.

The main apparatus elements required for carrying out this process are the unstabilizing heater, having means for supplying the oil under heavy pressure and for heating the oil to the point of unstable equilibrium; the pyrolysis chamber having means for heating the contents of the chamber to a temperature greater than the temperature in the tubes of th'e unstabilizing heater; the separating chamber which receives the oil from the 'pyrolysis chamber, and the condenser which recovers the liberated vapors. A cracking system including these elements, together with certain auxiliary apparatus, 'is shown in the accompanying drawing. in which Fig. l is asomewhat diagrammatic vertical sectional view of an apparatus in which the heat is supplied by gas or oil burners; and Fig. 2 is a similar view showing a modified form of pyrolysis chamber which is electrically heated. In the drawing, the numeral 2 indicates a tubular heater in which the oil is heated to the condition ot unstable equilibrium, 3 is the pyrolysis tube, 4 is the separating chamber or dephlegmator, and 5 is the condenser. The heater 2 preferably consists of straight `pipes 6 connected in series by shorter pipes 7 and provided at their ends with IIU removable plugs 8 which give access to the tubes 6 for inspection. The pipes composing the heater 2 are enclosed in a chamber E), suitably of brickwork, which is heated by means of one or more burners 10 controlled by a valve 11 and supplied with fuel through a pipe 12 from any suitable source, not shown. Oil is supplied to the pipes (i through a pipe 13 and a pump 14 which delivers the oil to the pipe 6 at high pressure which may be controlled by means of a valve 15. l do not wish to contine myself to the use of any particular pressure in the heater 2, since the pressure may be varied Within considerable limits, depending upon the character of the oil being treated. l have found, however, that improved results are obtained with increase ot' pressure up to pressures of the order ot' 1500 pounds -to the square inch. Further increase in pressure is of less advantage, but l consider that it is Within the scope ot my invention to employ any pressure in the preheatar upto ve thousand pounds or more per square inch.

The pipes 6 are preferably so connected that the oil enters at the upper part of the heating chamber and passes downwardly through the successive pipes of the heater toward the burner 10. rlt`he heat within this heater should be high enough to bring the oil to the condition of unstable equilibrium discussed above, and may with advantage be trom 700 h". to 9000 lF., depending on the oil used. ll have obtained excellent results in cracking gas oil with avsystem in which the temperature of the heater 2 is 820C lt., but it will ot course be understood that thisparticular temperature is illustrative only, and that considerable variation in temperature is permissible,.-depending upon the character of the oil being treated.

From the heater tubes 0 the oil is conduct- I ed through a pipe 10, provided with a valve btt 17, to the inlet end of the pyrolysis tube 3. rlhe pyrolysis tube is contained within a chamber 18 which, like the chamber 9, is composed of brick-work but is preferably separated trom the chamber 9, since the temperature in the pyrolysis'tube is to be maintained` higher than the temperature in the heater 2. As shown in ldig. l, the-tube 3 is heated by means ota gas or oil burner 19 supplied with fuel through a pipe 20 controlled by a valve 21. Other heating means may ot course be employed, the chier1 requirement being that the temperature ot the pyrolysis tube be materially greater than the temperature in the heater 2. The difference between the two temperatures is preferably about 100O F. to 800o F. ln the installation already mentioned, where the temperature in the prelieater was 820o lt., the temperature in the pyrolysis tube was kept at abou The pyrolysis tube 3 is led into the separating chamber Il and is preferably bent up ward or provided with an elbow connection 22 opening upwardly. Itl will be particularly noted that the. discharge end ot the tube 3 zles become clogged with carbon after .a

short time, and l intentionally make the discharge end ot the pyrolysis tube atleast as wide as the tube 3 in order to prevent such clogging.

The separating chamber 4 resembles an ordinary dephlegmating tower, and contains battles 23 tor promoting the separation of the fixed gases and vapors from the solid and liquid residues. l provide means for heating the chamber e, such means suitably consisting of a ring-burner 24 surrounding the chamber 4 near its lower end. The separating chamber is heated for the purpose of keeping the expanding cracked products at suitable temperature to complete their rearrangement and reach a condition' ot stable equilibrium before Ventering the condenser; to prevent the cracked vapors from condensing, and also tor the purpose of keeping liquid the residues which collect in the bottom of the chamber.

l also lind that the yield of light hydrocarbons is increased somewhat by heating the separating tower, the reason for this increase being probably that there is a very small pressure drop between the cracking tube and the tower, with consequent expan-A sion ot the vapors which will produce cooling and will condense Asome ot' the heavier vapors unless heat is added. However, the temperature in the separating chamber need not be as high as the temperature in the pyrolysis tube 3. i320O l?. to 840 is a suitable temperature for this chamber, when gas oil is being cracked under the conditions stated above, and produces an additional yield oit 5% to 10% ot products ot the gasoline type.

[t pipe 25, controlled by a valve 26, communicates with the bottom et the chamber 4g for drawing ed the tarry accumulations at intervals. A pipe 27 leads from the top of the chamber-tft and is inclined upwardly in order that any vapors which may' condense in the pipe 27 beterey reaching the condenser 5 may flow back into the chamber Lt.

l prefer to operate .the cracking and separating .Zones under the lowest practicable pressure1 in order that the pressure drop between the preheater and the cracking tube may be as great as possible. When operating the system in this manner, l provide a lll() alti high-pressure pump, indicated diagrammatically at 28, which draws the vapors and gases through the pipe 27 and delivers them to the condenser 5at a pressure which is preferably as high as can be obtained under commer-cial conditions of operation, such condensing pressure being, for example, 100 to 200 pounds per square inch. The outlet pipe 29 from the condenser 5 leads to suitable storage receptacles and is provided with a valve 30 for maintaining the pressure in the condenser. Other valves may be insert-ed in the system with a view to safety. Thus a valve 31 is preferably inserted in the pyrolysis tube 3, in order to isolate the pyrolysis tube and the separating chamber from each other in case of accident in any part of the apparatus.

If desired, the pump 28 may be omitted, and the valve 30 may be employed to maintain the cracking tube, separating tower and condenser under pressure sufficient to carry the cracked products through the system, such pressure being from 50 to 300 pounds per square inch. This method of operation is less desirable than the method-employing lower pressures in the cracking and separating zones, because of the smaller pressure drop between the preheater and the cracking zone for a given pressure in the preheater.

Another advantage of the method in which a pump or other mechanical means is employed for compressing the gases and vapors before condensation is that such a system produces consta-nt motion of the products in the cracking zone, and therefore causes substantial regularity in the ow of vapors to the condenser. This provides an element of regulation which is lacking in prior processes where back pressure is relied upon t0 carry the products through the system.

The apparatus shown in Fig. 2 diifers 'from that in Fig. 1` mainly in the construction of the pyrolysis tube 3 which is located vertically above and Within the separating chamber 4. Means for electrically heating the tube 3 are indicated diagrammatically by a resistance coil 35 which surrounds the tube 3. embedded in suitable insulation 36, and is connected to a suitable source of electric current. not shown. The outer part ol this pyrolysis tube may be enclosed in a shell 37 provided with a flange 3S for supporting the tube upon the cover 39 of the tower 4, It will be understood that the electric heating means may be otherwise arranged. Oil from the preheater is deliveredinto the upper end ot the tube 3 through a. pipe 16 controlled by a. valve 1721.

In this form of my device the gases and vapors are lcd'oHI from the reaction chamber 41 through a pipe 27, and are conducted to a condenser. not shown. The advantages ot' the form of apparatus shown in Fig. 2

are that the heat in the pyrolysis chamber may be more readily controlled, and also that most of the carbon which is liberated in the pyrolysis chamber falls by gravity into the chamber 4 and the deposit of carbon on the walls of the chamber 3 is thus greatly reduced. Balles 23, a ring burner 24, and a draw-off pipe 25 controlled by a valve 26' are provided, as in Fig. l.

Suitable doors are provided in the brick- Work enclosures to give access to the apparatus for cleaning and repair. Since such arrangements are common, it is not considered necessary to show them on the drawing.

Many different cracking processes have been proposed, but most of them cannot be used commercially because of the deposits of carbon which form in the cracking zonesvand which rapidly cause the apparatus to cease to function.

The process described above avoids such clogging, in large measure, by distributing the cracking or pyrolysis of the oil through several stages of the apparatus. First, unstable equilibrium is produced in a closely confined space and under such correlation of temperature and pressure that cracking cannot take place With its accompanying evolution of gases, vapors and carbon. This heating step, reaching as it does, the normal cracking temperature of the oil, but without exceeding its maximum critical temperature, induces a condition of strain on the hydrocarbon molecule Without producing any appreciable cracking. Upon suddenly releasing the pressure and simultaneously applying heat the equilibrium maintained by the high pressure is destroyed, and the molecules rearrange themselves, undergoing pyrolysis in the zone of intensified heat, under conditions of turbulence which tend to prevent deposition of carbon; and finally the cracking reaction is allowed to complete itself in the separating chamber 4 or 4,

rlhe apparatus is so adjusted that the oil is at its critical point of unstable equilibrium when it is delivered through the pipe 16 0r 16 into the pyrolysis tube 3 or 3a. The sudden reduction in pressure from 1000 to 3000 pounds down to a low or even negative pressure, with. addition o t heat, permits the disintegration ot the molecules that are in unstable equilibrium. but since the cracking tube 3 or 3 is still constricted in area the gases and vapors cannot yet readily escape. However, they are released in such a manner as to cause the violent turbulence in the cracking tube already mentioned, and this turbulence serves to carry most of the carbon that is produced along the cracking tube and into the reaction tower.

When the oil is permitted to suddenly eX- pand into the pyrolysis tube, some cracking might take place, even if the pyrolysis tube were not heated. However, the amount of lio etiective cracking at this point would be greatly reduced by the fact that `a sudden fall 1n temperature accompanies the reduction of ressure, and this fall in temperature would Q e great enough to neutralize to a considzone, have not been more, successful. I therefore heat the pyrolysis tube to restore the temperature of the expanded oil, and also kto increase its temperature above the point to which it has previously been heated. I

i consider that this 4isfperhaps the most iinportant feature of my invention, and contributes most largely ,to the increased yields of gasoline which I have obtained. By the addition of heat to the 4oil at the instant it is expanded, the conditions necessary to pyrolysis are not only maintained but are accentuated.

From the pyrolysis chamber, the oil is violently discharged into the separating tower. The separating tower is kept under the same nominal pressure as the cracking tube, but the suddenl removal of the confined walls about the turbulent oil permits the oil to burst into a tine mist when it enters the reaction tower, this condition being ideal for the release ot the fixed gases and volatile vapors which may have been originally present in solution in the oil, or have been evolved during the cracking process. The dephlegmating battles Z3-23a, however, prevent the gases and vapors from entraining any substantial amount of liquid, and the liquid falls to the bottom of the tower which, as stated above, is kept at a temperature suthcicnt to keep this liquid in a fluid condition.

From time to time the residues are drawn trom the bottom of the separating tower, and the plant should be so operated that approximately 20% to 40% of the original oil which is pumped in is removed as residue from the tower. The other 60% to 80% of the oil appears as distillate which carries from 60% to 80% of hydrocarbons of the gasoline type. Thus, in a plant of this kind, I obtain from 35% to 65% of marketable gasoline. whereas in other cracking processes only 20% to 30% are obtained. The reasons for this greatly increased yield are, first. the production in the heater of conditions necessary for rapid cracking. second, the removal of the oil from the heater with sudden drop in pressure, and with the instantaneous addition of heat to cause cracking. and third, the introduction ot the partly cracked oil into a. tower which 1s large with respect to the previous cracking zone, and which therefore permits the turbulent material to complete its crackingreaction and separate into volatile gases and residues.

Two crackin" tubes and two towers may be fed from a single unstabilizing heater, or, if desired two or more unstabilizing heaters may evidently be connected to feed one cracking tube. By employing two towers and two cracking tubes with a single unstabilizing heater and with suitable valves, the process can be made practically continuous, for while one cracking tube or tower is being cleaned the other is in use.

Little or no carbon should be deposited in the unstabilizing heater tubes, since no cracking is intended to occur there. However, cracking may sometimes, through accident, occur in this heater and it is desirable that the heater tubes shall be so constructed as to be readily inspected and cleaned if necessary.

Carbon is deposited in the cracking tube, but more slowly than in ordinary cracking tubes. In one apparatus of small capacity which I have operated, the cracking tube required cleaning after 500 gallons had passed through it. In the usual tubular type of cracking still ofthe same size only 200 gallons could be passed through the cracking tubes before the carbon would choke the tubes and render them useless.

The separating tower should be taken apart and cleaned at suitable intervals. In the apparatus just referred to, it was found necessary to clean the separating tower after 1200 gallons of oil had been treated. If the tower alone were used as a cracking unit, only 50 gallons could be passed through it before it would become choked with carbon. The reason for this difference is that the carbon produced in the cracking tube and carried with the oil into the separating tower is in a granular condition, and most of it is withdrawn with the heavy oil and tarry residues from the bottom of the tower. In time, however, the walls et the tower become coated with carbon and cleaning is necessary.

It is to be especially noted that the very superior results produced by this process are due in large part to the production of conditions necessary for pyrolysis, while so altering those conditions that the carbon which results from the 'decomposition of the hydrocarbons has no time to be deposited on the walls of the apparatus while in a very minute or molecular state. In this state it adheres closely to steel and rapidly builds up. By preventing the carbon from being liberated in actual contact with the enclosing walls until it has grown together into aggregates or granules, its tendency to attach itself to the walls of the apparatus substantially disappears and the c arbon is readily withdrawn from the reaction tower along the residual oil.

To illustrate my invention the following example, already mentioned above in general terms, is given in detail without, however, limiting my inventionV to theV particular temperatures or pressures stated, since these temperatures and pressures will, of course,

vary in accordance with the nature of the oil under treatment.

Oz'l treated-Gas oil.

Specific gravity of original oil-30 B.

Temperature in heater-808 F.

Pressure in heater-1190 pounds per square inch.

Temperature in 1050 F.

Pressure in cracking chamber-about 200 pounds.

cracking chamber-about Dz'sz'llatz'on range of original oil.

First drop, 110 C.

4.0%, 300 c. 95.5%, residue above 300 C. 0.5%, loss.

Destillation range of oz'Z deli/@ered from unstabz'lz'm'ng heater (determined by separate experiment, since direct determination. a commercial apparatus s impossible.

Distillatz'on range of same oz'Z when heated toy 812 F. wider pressure of pounds per square naht sp. gr. before distillation 33.1%.

First drop, 55 C.

62%, residue above 300 C.

1.5%, loss. Much carbon deposited.

This indicates the occurence of much cracking in the absence of high pressure.

In the claims, the expression critical cracking range means that range of temperature, for any given oil, between (1) the temperature at which cracking takes place under normal or low pressure of the order of 100 pounds per square inch, and (2) the temperature above which no practicable pressure will prevent substantial cracking. The expression maximum critical cracking temperature as used in the claims, refers to the upper temperature limit just mentioned, that is, the temperature, for any given oil, above which no pressure which can practically be applied will prevent cracking.

It is to be understood that the apparatus which I have shown and described may be varied in many respects without departing from my invention, the scope 'of which is set orth in the appended claims.

I claim as my invention:

1. In the cracking of relatively heavy'hydrocarbons to produce lighter hydrocarbons of the gasoline type, the step that comprises inhibiting the cracking of the hydrocarbons by applying pressure to the oil in addition to the vapor pressure of the oil while heatin the oil to a temperature within its critica cracking range said critical cracking range being defined as that temperature range within which cracking can be inhibited b pressure and which exists for 10 F. to 50 above the normal cracking range at low pressurels of the order of 100 pounds per square inc 2. The process of converting relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil to a temperature within its critical cracking range as defined in claim 1, subjecting said oil, while being so heated, to pressure sufficient to prevent substantial cracking in said oil, reducing the pressure on the oil and, simultaneously with said reduction in pressure, -adding suflicient heat to the oil to at least restore the heat lost through expansion.

3. The process of converting relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil to a temperature within its critical cracking range as defined in claim 1, subjecting said oil, while beingso heated, to a pressure .suiiicient to prevent cracking in said oil, reducing the pressure on the oil to a lower but still super-atmospheric pressure and, simultaneously with' said reduction in ressure, adding suiiicient heat to the oil to ring said oil to a temperature substantially above the temperature of said first heating step. y

4. The process of converting relatively high-boiling hydrocarbons that comprises heating a hydrocarbon oil to a temperature Within its critical cracking range as defined in claim 1, under a pressure suiiicient to prevent substantial cracking thereof, and delivering the oil to a cracking chamber maintained at a less pressure. and at a higher temperature than the pressure and temperature 1n said first heating step.

5. The process of converting relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil to a temperature within its critical cracking range as defined in claim 1, under pressure sufiicient to prevent substantial cracking, reducing the pressure on the oil and, simultaneously with said reduction in pressure, adding sufficient heat to the oil to at least compensate for the heat lost through expansion.

6. 'lhe process of converting relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil to a temperature within its critical cracking range as defined in claim 1, under pressuresuflicient' to prevent substantial'cracking, reducing the pressure on the oil to a lower but still super-atmospheric pressure and, simultaneously with said re' duction in pressure, adding suflicient heat to the oil to at least compensate for the heat lost through expansion.

7. rlhe process of converting relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil to a temperature within its critical cracking range as defined in claim 1, under pressure of the order of 1000 pounds per square inch and upward, reducing the pressure on the oil and, simultaneously with said reduction in pressure, adding sufficient heat to the oil to at least compensate for the heat lost through expansion.

8. The process fy converting relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil to a temperature within its critical cracking range as defined in claim 1, under pressure of the order of 1000 pounds per square inch and upward, reducing the pressure on the oil to a lower but still superatinospheric pressure and, simultaneously with said reduction in pressure, adding sufiicient heatyto the oil to at least compensate for the heat lost 'through expansion..

9. The process of converting relatively high-boiling 'hydrocarbons to lower-boiling hydrocarbons that'comprises heating a hydrocarbon oil to a temperature within its critical cracking range as defined in claim 1, under pressure sufficient to prevent substantial cracking, reducing the pressure on the oil and, simultaneously with said reduction in pressure, adding sufficient heat to the oil to at least compensate for the heat lost through expansion, said heat being added under conditions producing turbulence iii the oil.

10. The process of converting relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil vto a temperature within. its

critical cracking range as defined in claimy 1, under p'ressure sufficient to prevent substantial cracking, reducing the pressure on the' oil to a lower but still super-atmospheric pressure and, simultaneously with said reduction in pressure, adding suflicient heat to the oil to at least compensate for the heat lost through expansion, said heat being added under conditions producing turbulence in the oil.

11.- The process of convertingV relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil to a temperature within its critical cracking range as defined in claim 1, under pressure suiiicient to prevent substantial 'eracking, reducing the pressure on the oil and, simultaneously with said reduction in pressure, adding suiicient heat to the oil to at least compensatel for the heat lost through expansion, said heat being added under conditions producing turbulence in the oil, and then transferring the oil to a chamber of' relatively large diameter.

13. The process of' converting relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil to a temperature within its critical cracking range as defined in claim 1, under pressure sufficient to prevent substantial ciacking, reducing thepressure on the oil to a lower but still super-atmospheric pressure and, simultaneously with said reduction in pressure, adding sufficient heat to the oil to at least compensate for the heat lost through expansion, said heat being added under conditions producing turbulence in the oil, and then transferring the oil to a chamber of relatively large diameter.

14. The process of converting relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil to a temperature within its critical cracking range as defined in claim 1,

under pressure of the order of 1000 pounds per'square inch and upward, reducing the pressure on the oil, simultaneously adding suiiicient heat to the -oil to at least compen` sate for the heat lost through expansion, said heat being added under conditions producing turbulence in the oil, and then transferring the oil to a chamber of relatively large diameter.

15` The process of converting relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hy.

di-ocarbon oil in a confined zone to a tem` perature within its critical cracking range as defined in claim 1, under pressure sufficient fined in claim 1, under pressure of the order of 1000 pounds per square inch and upward. suddenly liberating the heated oil into a cracking zone with substantial drop in pressure, and heating said cracking zone ,above the temperature of the first heating zone to promote the cracking reaction thus induced.

17. The process of converting relatively high-boiling lhydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil in a confined zone to a ternperature within its critical cracking range as defined in claim 1, under pressure sufficient to prevent substantial cracking, suddenly liberating the heated oil into a cracking zone maintained under a lower but still super-atmospheric pressure, and heating said cracking zone above the temperature' of the first heating zone to promote the crackingreaction thus induced.

18. The process of converting'relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil in4 aconfined zone to atemperature of the first heating zone to promote the cracking reaction thus induced.

19. The process of converting relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil in a confined zone to atemperature within its critical cracking range as defined in claim 1,- under pressure sufficient to prevent substantial cracking, suddenly liberating the heated oil with substantial drop in pressure into a lrestricted cracking zone of somewhat larger diameter than the said heat-ing zone, and heating the said cracking zone to a temperature above the temperature of the first heating zone to promote the cracking reaction thus induced.

20. The process of converting relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil in a confined zone to atemperature within its critical cracking range as defined in claim 1, under pressure of the order of 1000 pounds per suddenly liberating t cheated oil with substantial drop in pressure into a restricted cracking zone of somewhat larger diameter than the said heating zone, and heating the said cracking zone to a temperature above the temperature of lthe first heating zone to promote the cracking reaction thus induced.

21. The process of converting relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil in a confined zone to a teinperature within its critical cracking range as defined in claim 1, under pressure sufficient to prevent substantial cracking, suddenly liberating the lieated oil, with drop in pressure to a lower but still super-atmospheric pressure, into a restricted cracking zone of somewhat larger diameter than the said heating zone, and heating the Asaid cracking zone to a temperatureabove the temperature of the first heating zone to promote the cracking yreaction thus induced.

22. The process of' converting relatively high-boiling hydrocarbons to lower-boiling` hydrocarbons that comprises heating a hydrocarbon oil in a confined zone to a temperature within its critical cracking range as defined in claim 1 under pressure sufficient to substantially prevent cracking, sud'- denly liberating the heated oil, with substantial drop in pressure, into a restricted cracking zone of somewhat larger diameter` than the said heating zone, maintaining the said cracking zone at a temperature above the temperature ofthe heating zone to promote the cracking reaction thus induced,

transferring the oil from the said cracking zone to a chamber of mater1ally greater diameter than the said cracklng zone, drawuare inch and upward,

ing ofi' vapors from the said chamber and condensing liquid hydrocarbons from said vapors.

23. The process of converting relatively high-boiling hydrocarbons to lower boiling hydrocarbons that-comprises heating a hydrocarbon oil in a confined zone to a temperature within its critical cracking range as defined in 4claim 1, under pressure of' the order of 1000 pounds per square inch and upward, suddenly liberating the'heated oily upward, suddenly liberating the'heated oil,

with drop in pressure to a lower but still super-atn'iospheric pressure, into a restricted cracking zone of somewhat larger diameter than the said heating zone, maintainin the said cracking zone at a temperature a ove the temperature of the heating zone to promote the cracking reaction thus induced, transferring the oil from the said cracking zone .to a heated chamber of materially greater diameter than the said cracking zone, drawing off vapors from the said chamber and condensing liquid hydrocarbons from said vapors.

25. The process -of converting relatively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises continuously introducing a hydrocarbon oil into a tubular heater heated to a temperature within the critical cracking range of the said oil as defined in claim 1, while maintaining said oil in said heater under pressure suicient to prevent substantial cracking, continuously liberating the heated oil into a restricted cracking zone of somewhat larger diameter than said tubular heater, maintaining said cracking zone under pressure materially less than the pressure in said tubular heater and at a temperature materially higher than the temperature of the oil in said heater, thereby promoting the cracking reaction and causingL turbulence in the oil through liberation of vapors and gases, continuously transferring the oil from said cracking zone to a chamber of materially greater diameter than said c rackinczone,`thereby atomizing the oil and separating vapors and gases from the residual oil and carbon, maintaining *said chamber at a temperature suiicient to prevent the lighter vapors from condensing through cooling by expansion, continuously drawing oli vapors and gases from said chamber and condensing light-boilin hydrocarbons therefrom, and periodically drawing on? residues from the bottom of said chamber.

26. The process ot converting rela-tively high-boiling hydrocarbons to lower-boiling hydrocarbons that comprises heating a hydrocarbon oil to at least 7 00o F., maintaining the oil while being so heated under pressuie of at least 1000 pounds per square inch, transmitting the heated oil into a restricted cracking chamber maintained under pressure materially less than the pressure under which said oil was initially heated, heating said cracking Ichamber suiliciently to at least restore the heat lost by the oil through expansion, and removing and recovering lower-boiling hydrocarbons .produced in said cracking chamber.

27. The process of converting relatively high-boiling hydrocarbons into lower-boiling hydrocarbons that comprises heating a hydrocarbon oil to a temperature between 7 00 F. to 900 F., maintaining the oil, While being so heated, under pressure of at least 1000 pounds per square inch, continuously transferring the preheated oil into a cracking chamber maintained under pressure of not over 300 pounds per square inch and heated sullciently to increase the temperature ofthe heated oil to a temperature at least 100 F. higher than its heated temperature, and removing and recovering the lowerboiling hydrocarbons produced in said cracking chamber.

28. The process of converting relatively high-boiling hydrocarbons into lower-boiling hydrocarbons that comprises heating'a hydrocarbon oil to a temperature ot' the order of 800 F., maintaining the oil, while being so heated, under pressure of at least 1000 pounds er square inch, continuously transferring t c heated oil into a cracking chamber maintained under pressure of the order of4 100 pounds er square inch, and heated sufiiciently to increase the temperature of the heated oil to a temperature of at least 100o F. higher than its heated temperature and removing and recovering the lower-boiling hydrocarbons produced .in said cracking chamber.

29. The process of converting relativel high-boiling hydrocarbons into lower boiing hydrocarbons that comprises continuously heating a hydrocarbon oil to a temperature within its critical cracking range as defined in claim l, maintaining the oil during said heating step under pressure sufficient to l oil from said cracking chamber through anl unrestricted opening into a chamber of larger diameter than said cracking chamber, removing vapors and fixed gases from the top of said chamber, and periodically removing residues from the bottom of said chamber.

30. The pr'ocess fof converting relatively high-boiling hydrocarbons into lower boiling hydrocarbons that comprises passing a hydrocabon oil through three successive heated zones, first, a heating zone where the oil is brought to a'temperature within its critical cracking range as defined in claim l under pressure suiiicient to prevent substantial cracking; second, a cracking zone where the heated oil is permitted to expand and is heated, simultaneously with such expansion, to promote the cracking reaction and to produce turbulence in the oil; and third, a separatng zone of much larger diameter than the preceding zones, drawing ofi' vapors and gases from said separating zone and condensing low-boiling hydrocarbons therefrom.

3l. The process of convertingrelatively high-boiling hydrocarbons into lower-boiling hydrocarbons that comprises heating a hydrocarbon oil to a temperature .within its critical cracking range as defined in claim l, maintaining said oil during said heating under pressure sufficient to prevent substantial cracking thereof, permitting the heated oil to expand, adding heat to the expanding oil sufficient to cause cracking therein, drawing oii' cracked products by means of suction, and condensing lighter-boiling hydrocarbons from the lighter constituents of the cracked products under pressure materially greater than the pressure in said cracking step.v

32. Apparatus for cracking hydrocarbons comprising a tubular heater, means for introducing oil under pressure into said heater, a cracking chambercommunicati-ng with said heater, said cracking chamber being of somewhat larger diameter than the tubes of said heater, a separating chamber of relatively large diameter communicating with said `cracking chamber, and means for heating said heater, said cracking chamber, and said separating chamber.

33. Apparatus for cracking hydrocarbons comprising a tubular heater, means for introducing oil under 'pressure into said heater, a cracking chamber communicating with said heater, said cracking chamber 'being of somewhat larger diameter'than the tubes of said heat-er, a separating chamber of relatively large diameter communicating with said cracking chamber through lan opening at least as large as the diameter 'of said cracking chamber, and independent' means for heating said heater, said cracking chamber, and said separating chamber.

34. Apparatus for cracking hydrocarbons comprising a tubular heater, means for introducing oil under pressure into said heater, a cracking chamber communicating with said heater, said cracking chamber being of somewhat larger dia-meter than the tubes of said heater, a separating chamber of relatively larger diameter communicating with said cracking chamber through an opening at least as large as the diameter of said cracking chamber, independent means for heating said heater, said cracking chamber, and said separating chamber, baffles disposed in said separating chamber, means for withdrawing vapors and gases from the top of said separating chamber and for condensing light-boiling hydrocarbons therefrom, and means for withdrawing residues from theV bottom of said chamber.

35. Apparatus for cracking hydrocarbons comprising a heater composed of a plurality of straight, horizontal lengths of pipe connected in a vertical series by short vertical pipes and having removable plugs giving accefis to said pipes, a pump connected to introduce oil under pressure into the up per pipe, a Vertical pipe communicating with the lower pipe and connected with a cracking chamber of'larger diameter than the pipes composing said heater, a valve for controlling the sudden release of pressure on the oil as it enters said cracking chamber, and means for separately heating said heater tubes and said cracking chamber.

36. Apparatus for cracking hydrocarbons comprising a heater composed of a plurality of straight,- horizontal lengths of pipe connected in series by short vertical pipes and having removable plugs giving access to said pipes, a pump connected to introduce oil under pressure into the upper pipe, heating means disposed beneath the lower pipe, a Vertical pipe communicating with said lower pipe, a cracking chamber communicating with said vertical pipe, said cracking cham.

ber being of larger diameter than the pipes composing said heater;` a valve for controlling the discharge of oil into said cracking chamber, 'means for heating said cracking chamber, a separating tower of materially larger diameter than the said cracking chamber and communicating therewith through ,an opening at least as large as the internal diameter of said cracking chamber, means for drawing o' vaporsfrom the top of said tower, means for drawing oit residues from the bottom of said tower, and means for heating said tower.

y 37. Apparatus for cracking hydrocarbons "comprising a heater composed of a plurality of straight, horizontal lengths ot pipe connected in series by short vertical pipes and .having removable plugs giving aece"s to 'sald pipes, a pump connected to introduce oil under pressure into the upper pipe, heating means disposed beneath the lower pipe, a vertical pipe communicating with said lower pipe, a cracking tube communicating with said vertical pipe, said cracking tube being of larger diameter than the pipes composing said heater. a valve for controlling the discharge of oil into said cracking tube, means for heating said cracking tube, a separating tower of materially larger dialneter than the said cracking tube and communicating' therewith through an opening at least as large as the internal diameter of said cracking tube, a pipe communicating with the upper part of said tower and leading to a. condenser, a valve in the discharge pipe from said condenser, whereby saidl condenser may be maintained under pressure, means for heating the said separating tower, and means for drawing oit' residues from the bottom of said tower.

38. Apparatus for cracking hydrocarbons comprising a tubular heater, a pump for forcing yoil under pressure through said heater, a pipe leading from said heater and provided with a valve, for suddenly releasing pressure on the oil, a vertical tubular cracking chamber connected to receive oil from said pipe, means for electrically heating said cracking chamber, al separating tower with which said cracking chamber is in free communication, means for heating the said tower, means for drawing olf vapors and gases from the upper part of said tower, and means for drawing oli' residues from the bottoni of said tower.

39. Apparatus for cr'acking hydrocarbons comprising a tubular heater, a tubular cracking chamber adapted to receive' oil from said heater, a valve interposed bet tween said heater and said cracking chamber to permit sudden release of the ressure in said heater, a separating c am-V ber communicating with said cracking chamber, a plpe for drawing ofi' vapors and gases from said chamber, means connected to draw off said gases and vapors through said pipe, a condenser connected to receive said gases and vapors from said drawing olf means, said drawing oil` means being capable of regulatiner the pressures in the said cracking cham er and in said condenser to maintain said pressures substantially constant and to maintain a. substantially constant difference in pressure between said cracking chamber and said condenser.

40. The process of converting relatively high-boiling hydrocarbons into lower-boiling hydrocarbons, which comprises raising a high-boiling hydrocarbon oil in liquid phase to a cracking temperature while subjected to pressure of the order of 1000 pounds per square inch and upwards sufiicient to prevent substantial cracking, and releasing the heated oil into a cracking zone' where there obtains lower pressure causing the oil .to enter a state of fine subdivision and where there obtains a temperature causing cracking of the oil while in said state of fine subdivision to form lower-boiling hydrocarbon oils.

41. The process of converting relativel high-boiling hydrocarbons into lower-boi ing hydrocarbons, which comprises raising a high-boiling hydrocarbon oil in li uid phase to a cracking temperature while su jected to pressure of the order of 1000 pounds per square inch and upwards sufficient to prevent substantial cracking, and releasing the heated oil into a cracking zone where there obtains lower pressure causing the oil to enter a state of line subdivision and where there obtains'a temperature higher than that attained by the oil while in the liquid phase to cause cracking of the oil while in said state of fine subdivision to form lower-boiling hydrocarbon oils.

42. The process of converting highdooiling hydrocarbons into lower-boiling. hydrocarbons, which comprises subjecting a highboiling hydrocarbon oil while in liquid phase t-o a cracking temperature and to pres sure ofthe order of 1000 pounds per square inch and upwards to prevent substantial cracking, and thereafter releasing the heated Aoil into a region of materially lower but lsubstantially superatmosphericfpressure and there effecting cracking thereo u 43. The process of converting high-boiling hydrocarbons into lower-boiling hydrocarbons which comprises subjecting a highboiling hydrocarbon-oil while in the liquid phase to a cracking temperature of 700 to 900 F. and to a pressure -of the order of 1000 pounds per square inch whereby cracki-ng is prevented, and then delivering the heated oil into an enlarged zone at a substantially reduced pressure but increased temperature where cracking is effected in the vapor phase. y

44. A process of converting high boiling hydrocarbon oils into lower boiling products that comprises heating the oil to a cracking temperature of from 700 to 900 F. in transsit through a heated coil pf restricted crosssection while maintained in the liquid hase at a pressure of the order of 1000 poun s per square inch and upwards, delivering the oil into a short tube of greater cross-section maintained under a materially lower pressure where the oil is largely vaporized, and delivering the products from said tube into an enlarged chamber maintained at a pressure not higher than in said tube where separation of the evolved vapors from liquid oil takes place.

45. A process of converting high boiling hydrocarbon oils into lower boiling products that comprises heating the oil to a cracking temperature of from 700 to 900 F., in transit through a heated coil of restricted crosssection while maintained in the liquid phase at a pressure of the order of 1000 pounds per square inch and upwards, delivering the oil into a short tube of greater cross-section 'maintained under a materially lower pressure where the oil is largely vaporized, delivering the products from said tube into an enlarged chamber maintained at a pressure not higher than inI said tube where separation-.of the evolved vapors from liquid oil takes place, retluxing heavier constituents of the vapors to the body of the liquid in said separating chamber and condensing the lighter constituents of the evolved vapors.

46. A process of converting high boiling hydrocarbon oils into lower boiling products that comprises heating the oil to a cracking temperature of from 700 to 900 F. in transit through a heated coil of restricted crosssection while maintained in the liquid phase at a pressure of the order of 1000 pounds per square inch and upwards, delivering the oil into a short tube of greater cross-section maintained under a materially lower pressure where the oil is largely vaporized, delivering the products from said tube into an enlarged chamber maintained at a pressure not hlgher than in said tube where separation of the evolved vapors from liquid oil takes place, refluxing heavier constituents of the vapors to the body of the liquid in said separating chamber, condensing the lichter constituents of the evolved vapors un er a pump pressure materially greater thanthatl existing in, said separating chamber and withdrawing liquid oil from said separating chamber.

47. Apparatus for converting high boiling hydrocarbon oil into lower boiling products that comprises a highly heated elongated coil of restricted cross-section maintained under high pressure, a short tube of larger cross-section connected therey products comprisingan elongated heating coil of restricted cross-section set in a furnace and maintained under a pressure of the order of 1000 pounds per square inch, a short cracking tube of larger cross-section set in a se arate furnace and connected to said coil t rough a pressure-reducing valve, an enlarged separating chamber set in a separate furnace for receiving the material from said short tube through a connection having a discharge opening of greater area than the cross-section of the tube, and means fory removing the evolved vapors from said chamber.

49. Apparatus for converting high boiling hydrocarbon oils into lower boiling products that comprises an elongated coil of restricted cross-section and a short tube of greater cross-section connected in series relation with a pressure-reduciner valve interposed between them, a furnace for heating the coil, electrical heating means surrounding the tube for subjecting it to heat, an enlarged separating chamber into which a substantial portion of the tube projects and means for withdrawing evolved vapors from said chamber.

50. The process of converting high boiling hydrocarbonoil into lower boiling products that comprises continuously forcing-oil in liquid form through an extended coll of restricted cross section under a pres-` sure of the order of 1000 pounds per square inch and upwards, heating the oil in its passage through the coil to a cracking temperature of not more than 900o F., said temperature and pressureconditions tending to inhibit cracking in the coil, delivering the heated oil from the coil directly and without cooling into an enlarged cracking chamber maintained under a substantial superatmospheric pressure but materially reduced below that of any part of the coil while maintaining the oil therein at a cracking temperature in excess of 700 F. to effect cracking and vaporization of a portion thereof in said chamber, and withdrawing the evolved vapors therefrom.

In testimony whereof I the said JAMES M. SonooNMAKER, JR., have hereunto set my hand.

JAMES M. SCHOONMAKllR, JR. 

